JP7047421B2 - Transport device and image forming device - Google Patents

Description

The present invention relates to a transport device and an image forming device.

Recently, even in the commercial printing industry, in small lot and high-mix variable data printing, the shift from conventional offset printing to on-demand printing such as an electrophotographic image forming apparatus is progressing. In order to meet this need, electrophotographic image forming apparatus is required to have image quality comparable to that of an offset printing machine.

In an electrophotographic image forming apparatus for forming a color image, an image formed on a plurality of image carriers is primarily transferred to one endless intermediate transfer belt, and then the primary transfer image on the intermediate transfer belt is transferred to a transfer sheet or the like. In general, a method of batch secondary transfer to the recording medium of the above is used. Therefore, in order to secure the above-mentioned high-quality image, the stability of the moving speed of the intermediate transfer belt on which the monochromatic toner images from the plurality of image carriers are sequentially transferred is very important. This is because when the movement speed fluctuation of the intermediate transfer belt is large, the positions where the toner images of each color are transferred are relatively displaced, and the image is output as a color-shifted image.

As the above-mentioned intermediate transfer belt, it operates by adding a scale in which indexes having different reflectances are arranged at regular intervals to the entire circumference thereof, or by directly engraving the indexes on the belt surface at regular intervals with a laser or the like. Among them, there is known one in which an optical sensor reads the interval at which an index passes and feedback control is performed on a drive motor so that speed fluctuation does not occur to prevent the occurrence of color shift.
Due to the characteristics of the optical sensor used for the feedback control described above, it is necessary to provide a distance from the index of the intermediate transfer belt within a predetermined range. For this reason, if the distance between the two is different or if the distance between the two is not stable while the intermediate transfer belt is running, feedback control becomes impossible or operation is performed without normal control. The speed of the transfer belt may fluctuate and color shift may occur.
Therefore, in order to stabilize the distance between the optical sensor and the intermediate transfer belt, a technique for urging the sensor holding member holding the optical sensor by a coil spring is disclosed (see, for example, "Patent Document 1").

In the technique disclosed in "Patent Document 1", the intermediate transfer belt is wound around the transport rollers, but since the optical sensor is arranged on the outside between the transport rollers, the toner pattern on the belt is recognized. Since foreign matter such as toner scattered on the surface of the sensor adheres to the surface of the sensor, there is a problem that an adhesion prevention mechanism or a cleaning mechanism is required.
An object of the present invention is to provide a transport device and an image forming device capable of achieving running stability of a belt with a simple configuration without increasing the cost.

The invention according to claim 1 has a runnable endless belt having an index on an inner peripheral surface, a plurality of rollers supporting the belt, and a detecting means for detecting the index, and is based on the detecting means. A conveyor that controls the traveling speed of the belt based on the detection of the index, wherein the endless belt is an intermediate transfer belt.
Of the plurality of rollers that support the intermediate transfer belt, one is a drive roller.
A space portion and an outer ring portion are provided in all of the plurality of rollers.
All of the plurality of rollers are divided into a plurality of rollers in the direction of the center axis of rotation.
When viewed in the direction of the rotation center axis of the roller, the detection means is arranged in a space portion of a portion divided into a plurality of parts in the rotation center axis direction of the drive roller, and the detection means arranged in the space portion is a plurality. Optical sensor,
The index and the optical sensor are characterized in that they are relatively positioned with respect to the rotation center axis.

According to the present invention, since the detection means is arranged inside the roller on which the belt is hung, the relative distance between the belt and the detection means can be determined without the need for a member for pressing the belt against the rollers. Can be constant. This prevents the occurrence of various problems such as belt running resistance and load fluctuations, belt tension fluctuations due to these, and belt surface wear, improving belt running stability and reducing the number of parts. Therefore, the cost can be reduced and the assembly man-hours can be reduced.

It is a schematic block diagram of the transfer apparatus to which one Embodiment of this invention was applied. It is a C arrow view in FIG. FIG. 2 is a cross-sectional view taken along the line DD in FIG. It is a schematic diagram of the image forming apparatus to which one Embodiment of this invention is applicable. It is a schematic block diagram of the conventional transfer apparatus. It is the schematic which looked at the intermediate transfer belt shown in FIG. 5 from the inner peripheral surface side. It is a side view which shows the conventional optical sensor. It is a schematic diagram explaining the position of the intermediate transfer belt which changes by the image formation mode in the conventional transfer apparatus. It is a schematic block diagram of the conventional optical sensor which changes the position according to the intermediate transfer belt which changes the position.

First, prior to the description of the present invention, problems in the conventional transfer apparatus will be described.
In FIG. 5, which shows the main configuration of the conventional image forming apparatus, reference numeral 50 is a transfer device, reference numeral 51 is a photoconductor drum which is an image carrier for image forming in yellow, and reference numeral 52 is a photoconductor for forming a magenta image. Reference numeral 53 indicates a drum, reference numeral 53 indicates a photoconductor drum for forming a cyan image, reference numeral 54 indicates a photoconductor drum for forming a black image, reference numeral 55 indicates a fixing device, and reference numeral 56 indicates a resist roller pair.

The transfer device 50 as a transfer device includes an intermediate transfer belt 57, a primary transfer roller 58, 59, 60, 61, a secondary transfer roller 62, and the like.
The intermediate transfer belt 57 is hung on the rollers 63, 64, 65, 66 rotatably supported on the side plate of the transfer device (not shown) and the primary transfer rollers 58, 59, 60, 61, respectively, while maintaining a predetermined tension. The roller 66 is rotationally driven in the clockwise direction in FIG. 5 by a drive means (not shown) connected to the roller 66, which is a drive roller, so that the roller 66 is driven to travel in the direction indicated by the arrow A in FIG. .. Further, the roller 65 is arranged to face the secondary transfer roller 62 via the intermediate transfer belt 57, and functions as a secondary transfer opposed roller.

The fixing device 55 has a heating roller 55a and a pressure roller 55b, and a heat source such as a heater (not shown) is provided inside the heating roller 55a, and the pressure roller 55b is designated by a urging means (not shown). It is pressure-welded to the heating roller 55a.
The resist roller pair 56 arranged on the upstream side of the secondary transfer roller 62 in the sheet transport direction is prepared by first stopping the sheet S as a recording medium fed from a paper feed device (not shown) at its nip portion. The paper is fed to the secondary transfer nip portion, which is the nip portion between the secondary transfer roller 62 and the roller 65, at a predetermined timing.

From the above configuration, the toner image formed on the rotating photoconductor drums 51, 52, 53, 54 is placed on the intermediate transfer belt 57 traveling by the primary transfer rollers 58, 59, 60, 61. It is superimposed and transferred as a full-color toner image. After that, the sheet S is fed by the resist roller pair 56 at the timing matching the full-color toner image on the intermediate transfer belt 57, so that the full-color toner image is collectively generated on the sheet S at the secondary transfer nip portion. Next transfer is performed to form a full-color toner image on the sheet S. The sheet S on which the full-color toner image is formed is sent to the fixing device 55 to fix the full-color toner image by heat and pressure, and then is discharged to the outside of the machine.

In the configuration of FIG. 5, light is emitted and reflected toward the inner peripheral surface of the belt on the inner peripheral surface side of the intermediate transfer belt 57 and on the upstream side of the photoconductor drum 54 for forming a black image in the belt traveling direction. An optical sensor 67 for detecting light is arranged. The traveling speed of the intermediate transfer belt 57 is detected by detecting an index to be described later formed on the inner peripheral surface of the intermediate transfer belt 57 by the optical sensor 67. Then, based on this detection result, the operation of the driving means (not shown) for driving the roller 66 is controlled to control the traveling speed of the intermediate transfer belt 57, whereby the occurrence of each color shift is prevented.
The reason why the optical sensor 67 is arranged in the vicinity of the photoconductor drum 54 for forming a black image is that the black image is formed more frequently than the images of other colors, and the black image position is the reference of the other color image forming position. Because.

FIG. 6 is a view of the intermediate transfer belt 57 as viewed from the inner peripheral surface side. A scale 68 is formed over the entire circumference in the vicinity of one end on the inner peripheral surface of the intermediate transfer belt 57, and a plurality of indexes 69 having a reflectance different from that of the scale 68 are arranged in the scale 68 at regular intervals. It is set up. In this example, each index 69 is added to the inner peripheral surface of the intermediate transfer belt 57, but each index 69 may be directly engraved on the inner peripheral surface of the intermediate transfer belt 57 by a laser or the like.

FIG. 7 is a side view of the optical sensor 67. The optical sensor 67 has a light emitting element 67a and a light receiving element 67b, and the light emitted from the light emitting element 67a receives the reflected light reflected by the scale 68 by the light receiving element 67b, and the presence or absence of the index 69 is determined by the difference in the amount of light received. Is detected. Therefore, it is necessary to maintain the position accuracy so that the distance from the 68th surface of the scale to the optical sensor 67 is equal to the focal lengths of light emission and light reception.
When the intermediate transfer belt 57 travels at a constant speed, the time interval for detecting the presence or absence of the index 69 also becomes constant, but when the traveling speed of the intermediate transfer belt 57 fluctuates, the time interval for detecting the index 69 also fluctuates. Therefore, an intermediate transfer is performed by generating a control signal having an opposite phase speed by a control means (not shown) based on the detected time interval data and controlling the rotation speed of the drive means (not shown) for rotationally driving the roller 66. The traveling speed of the belt 57 is controlled.

In the transfer device 50, the intermediate transfer belt 57 is configured to be movable in a direction different from the traveling direction thereof, and in that embodiment, a full-color image is formed using all the photoconductor drums 51, 52, 53, 54. A mode, a monochrome mode in which an image is formed using only the photoconductor drum 54 for forming a black image, and a separation mode in which the intermediate transfer belt 57 is separated from all the photoconductor drums 51, 52, 53, 54 except during image formation. There are various aspects such as.

As an example, the position shown by the solid line in FIG. 8 indicates the position of the intermediate transfer belt 57 in the full color mode, and the position indicated by the broken line indicates the position of the intermediate transfer belt 57 in the monochrome mode. In the transfer device 50, the primary transfer rollers 58, 59, 60 are movably supported on the transfer device side plate (not shown), and the primary transfer rollers 58, 59, 60 are the corresponding photoconductor drums 58, 59, respectively. With respect to 60, it is configured to be able to be connected and separated at the same time by a contact and separation means (not shown). Therefore, since the traveling position of the intermediate transfer belt 57 changes in each mode, the optical sensor 67 is configured to be movable according to the traveling position of the intermediate transfer belt 57.

FIG. 9 shows the mounting structure of the optical sensor 67. The optical sensor 67 is fixed on the sensor holding member 70 and is configured to maintain a constant distance from the index 69 formed in the scale 68 on the intermediate transfer belt 57 as described above. Specifically, the sensor holding member 70 is fixed to the arm 71, and the arm 71 is swingably supported by the immovable member 72 constituting the transfer device 50. The immovable member 72 is configured so that its position does not change even when the primary transfer rollers 58, 59, 60 are moved.

The arm 71 having an L-shape has its bent portion supported by the immovable member 72 by a support shaft 73, and is configured to be swingable in the direction indicated by the arrow B in FIG. One end of the tension spring 74 that urges the end portion downward is attached to the end portion of the arm 71 on the one end side to which the optical sensor 67 is attached, and the other end of the tension spring 74 is an immovable member 72. It is fixed to. On the other end side of the arm 71, a cam 75 rotatably supported by the immovable member 72 and rotated by the motor 76 is arranged so as to come into contact with the other end of the arm 71.
With this configuration, the motor 76 is rotationally driven according to the amount of movement of each of the primary transfer rollers 58, 59, 60, and the arm 71 is swung to keep the distance between the optical sensor 67 and the inner peripheral surface of the intermediate transfer belt 57 constant. It will be possible to keep it at.

However, in the above configuration, for the positioning of the arm 71 in the arrow B direction, the angular position accuracy of the cam 75, the position accuracy of the support shaft 73, the position accuracy from the support shaft 73 to the sensor holding member 70, and the sensor holding member 70. In order to secure the position accuracy of the optical sensor 67, such as the mounting position accuracy of the optical sensor 67, dimensional accuracy, assembly accuracy, etc. of many parts are required, which increases the cost and requires a large number of assembly steps. ..
Further, since the traveling position of the intermediate transfer belt 57 changes according to the image formation mode, the rotation angle of the cam 75 is changed by a predetermined amount in order to move the position of the optical sensor 67 accordingly. Since the rotation angle of the arm 71 changes due to the component accuracy of the cam 75 and the error of the contact position with the arm 71, it is necessary to secure the assembly position accuracy of these parts, which increases the cost.

An embodiment of the present invention that solves the above-mentioned problems will be described below.
In FIG. 1, reference numeral 1 indicates a photoconductor drum which is an image carrier. On the left side of the photoconductor drum 1 for a black image, a plurality of photoconductor drums for other colors (not shown) are arranged in the same manner as in the conventional configuration shown in FIG. A primary transfer roller 2 is disposed below the photoconductor drum 1, and an intermediate transfer belt 3 which is an endless belt is disposed between the photoconductor drum 1 and the primary transfer roller 2.

The transfer device 4 as a transfer device having the intermediate transfer belt 3 is a plurality of primary transfer rollers 2 and an intermediate transfer belt 3 provided corresponding to each photoconductor drum 1 in the same manner as the transfer device 50 shown in the prior art. , A plurality of rollers including a drive roller 5 for tensioning the intermediate transfer belt 3, a secondary transfer roller (not shown), and the like. Similar to the transfer device 50, in this transfer device 4, each primary transfer roller (not shown) other than the primary transfer roller 2 is movably supported on a transfer device side plate (not shown), and each primary transfer roller (not shown) corresponds to each. The photoconductor drum (not shown) is configured to be able to be brought into contact with each other at the same time by a contact / detachment means (not shown) as the image forming mode changes.

In the present embodiment, the optical sensor 6 which is a detection means formed on the intermediate transfer belt 3 and is a detection means for detecting an index to be described later is arranged inside the drive roller 5 when viewed in the direction of the rotation center axis. Similar to the conventional technique, the photoconductor drum 1 for a black image serves as a reference for the image position of another color, and each primary transfer roller (not shown) moves and the intermediate transfer belt 3 moves as the image formation mode changes. The position of the drive roller 5 does not change even when the drive roller 5 is used. Therefore, by disposing the optical sensor 6 inside the drive roller 5, the relative position between the index formed on the intermediate transfer belt 3 and the optical sensor 6 does not change before and after the movement of the intermediate transfer belt 3. It becomes.
The mounting structure of the optical sensor 6 will be described below.

FIG. 2 is a view of the inner peripheral surface of the drive roller 5 as viewed from the arrow C side shown in FIG. A scale 7 is formed in the vicinity of the end portion of the inner peripheral surface of the intermediate transfer belt 3 with a constant width over the entire circumference thereof, and an index 8 having a reflectance different from that of the scale 7 is formed in the scale 7 at regular intervals. Multiple are formed. In the present embodiment, each index 8 is added to the inner peripheral surface of the intermediate transfer belt 3, but each index 8 may be directly engraved on the inner peripheral surface of the intermediate transfer belt 3 by a laser or the like.

The drive roller 5 that supports the intermediate transfer belt 3 is rotationally driven in the clockwise direction in FIG. 1 by a drive means (not shown) to drive the intermediate transfer belt 3 that is hung. At a position corresponding to each index 8 formed on the intermediate transfer belt 3 of the drive roller 5, a space portion 5a for preventing contact between the peripheral surface thereof and each index 8 is formed. On the axially outer side of the drive roller 5 than the space portion 5a of the drive roller 5, an outer ring portion 5b formed so as to have the same diameter as the drive roller 5 and supporting the peripheral edge portion of the intermediate transfer belt 3 is formed by the support shaft 5c. It is integrally formed with the drive roller 5.
One end of the support shaft 5c is rotatably supported by a bearing 10 fixed to a holding frame 9 which is an immovable member constituting the frame of the transfer device 4, and the other end of the support shaft 5 is also shown in the figure. It is rotatably supported by a bearing (not shown) supported by an immovable member. A rotational driving force from a driving means (not shown) is transmitted to the support shaft 5c, whereby the driving roller 5 is rotationally driven.

The optical sensor 6 having the light emitting element 6a and the light receiving element 6b is arranged at a position corresponding to the space portion 5a, and receives the reflected light reflected by the scale 7 which is a detection medium for the light emitted from the light emitting element 6a. Light is received by the element 6b, and the presence or absence of the index 8 is detected from the difference in the amount of light received.
When the intermediate transfer belt 3 travels at a constant speed, the cycle for detecting the presence or absence of each index 8 is also constant, but when the traveling speed of the intermediate transfer belt 3 changes, the cycle for detecting each index 8 also changes. Therefore, based on the data of the detected period, a control signal having a speed of opposite phase is generated by a control means (not shown), and the operation of the drive means (not shown) is controlled based on this control signal to control the intermediate transfer belt. The running speed of 3 is controlled.

FIG. 3 shows a cross-sectional view taken along the line DD in FIG. The optical sensor 6 is detachably attached to the optical sensor holding member 11, and the optical sensor holding member 11 is fixed to the holding frame 12 constituting the frame of the transfer device 4 by screws 13. The optical sensor holding member 11 is provided with a hole 11a into which the support shaft 5c can be fitted, so that the support shaft 5c and the hole 11a are fitted without a gap and the support shaft 5c is rotatably configured. A bearing that rotatably supports the support shaft 5c may be provided on the optical sensor holding member 11 as long as the error in position accuracy allows. Further, the optical sensor holding member 11 and the holding frame 12 may be fixed by welding or the like.

The distance from the center of the hole 11a to the fixed surface of the optical sensor 6 is the distance from the center of the support shaft 5c to the light emitting element 6a and the light receiving element 6b of the optical sensor 6 by processing with high accuracy within the processable range. Is secured with high accuracy.
Further, the outer ring portion 5b is also machined with high precision within a range that can be machined from the center of the support shaft 5c, and the distance to the scale 7 and the index 8 formed on the sandwiched intermediate transfer belt 3 is always high precision. It is secured.
From the above configuration, the mutual distance between the light emitting element 6a and the light receiving element 6b of the optical sensor 6 and the scale 7 and the index 8 is ensured with high accuracy, and the above-mentioned mutual distance is ensured due to vibration, movement, etc. of the intermediate transfer belt 3. Each index 8 can be stably detected by the optical sensor 6 without being affected by the above, and the traveling control of the intermediate transfer belt 3 can be stably performed.

As described above, according to the present invention, since the optical sensor 6 is arranged inside the drive roller 5 on which the intermediate transfer belt 3 is hung in the direction of the rotation center axis, the intermediate transfer belt 3 is supported by the drive roller. The relative distance between the intermediate transfer belt 3 and the optical sensor 6 can be made constant without the need for a member that presses against 5. This prevents various problems such as running resistance and load fluctuation of the intermediate transfer belt 3, tension fluctuation of the intermediate transfer belt 3 and surface wear of the intermediate transfer belt 3 due to these, and improves running stability of the belt. can do.
Further, since the number of parts is reduced, the cost can be reduced and the assembly man-hours can be reduced.

In the above-described embodiment, since the optical sensor 6 is arranged inside the drive roller 5 which is a member for driving the intermediate transfer belt 3 in the direction of the rotation center axis, the change in the traveling speed of the intermediate transfer belt 3 has a time lag. It can be detected almost directly without any problem, the traveling speed of the intermediate transfer belt 3 can be controlled in a short time, and the traveling speed of the intermediate transfer belt 3 can be kept constant at all times.
Further, in the above embodiment, the intermediate transfer belt 3 is movable in a direction different from the traveling direction, but the present invention can be applied to a configuration in which the intermediate transfer belt 3 is not movable. Further, in the configuration in which the intermediate transfer belt 3 is movable, the optical sensor 6 is arranged inside the drive roller 5 whose relative distance to the intermediate transfer belt 3 does not change before and after the movement of the intermediate transfer belt 3. , The above-mentioned effects can be obtained regardless of the movement of the intermediate transfer belt 3.

In the above embodiment, the drive roller 5, which is one of the rollers supporting the intermediate transfer belt 3, is provided with the space portion 5a and the outer ring portion 5b. However, all the rollers supporting the intermediate transfer belt 3 have the space portion. And may be configured to provide an outer ring portion. With this configuration, all the rollers do not interfere with the scale 7 and each index 8 when the intermediate transfer belt 3 is running, so that foreign matter such as toner scatters with the scale 7 and each index 8 and each roller. It is possible to prevent the scale 7 and each index 8 from being caught in the space, and it is possible to prevent the scale 7 and each index 8 from being scratched or soiled. As a result, it is possible to prevent a decrease in the reflectance in the scale 7 and each index 8, and it is possible to prolong the life.

Further, in the above embodiment, the configuration is shown in which the space portion 5a and the outer ring portion 5b are provided on the end side in the rotation center axis direction of the drive roller 5, but the drive roller 5 is divided into a plurality of parts in the rotation center axis direction. The optical sensor 6 which is a detection means may be arranged in the space of the divided portion. At this time, a plurality of optical sensors 6 may be arranged.
Further, as described above, all the rollers supporting the intermediate transfer belt 3 may be divided into a plurality of rollers in the respective rotation center axis directions, and the detecting means may be arranged in the divided portions.

Next, an image forming apparatus to which the transfer apparatus 4 shown in the embodiment of the present invention can be applied will be described. FIG. 4 shows a color printer as an image forming apparatus to which one embodiment of the present invention can be applied. In the figure, the color printer 14 is an electrophotographic color image forming apparatus that forms a color image by a plurality of image forming units 15 which are tandem type image forming portions, and the image forming unit 17 is inside the apparatus main body 16. It has a paper feed unit 18, a transfer device 4 as a transfer unit, a fixing unit 19, and a paper discharge unit 20.

The image forming unit 17 forms a special (S) toner image, which is a characteristic color such as colorless and transparent or white, in addition to the four colors of yellow (Y), magenta (M), cyan (C), and black (K). It is composed of five image-forming units 15S, 15Y, 15M, 15C, and 15K to be output. Each image forming unit 15 functioning as an image forming means uses special toners, yellow toners, magenta toners, cyan toners, and black toners having different colors as image forming materials, but the configurations other than these toners are the same. It will be replaced when it reaches the end of its life. Each image forming unit 15 can be attached to and detached from the apparatus main body 16, and each constitutes a process cartridge. Hereinafter, each image forming unit 15 will be described by taking as an example an image forming unit 15K that forms a black toner image.

The image forming unit 15K includes a charging device 21K, a photoconductor drum 1K as an image carrier, a developing device 22K, a static elimination device 23K, a photoconductor cleaning device 24K, and the like. These devices are held in a unit main body which is a common holding member, and by integrally attaching and detaching the unit main body to the device main body 16, each of the above-mentioned devices can be exchanged at the same time.
An exposure apparatus 25 is arranged above each image forming unit 15. The exposure apparatus 25 exposes and scans the photoconductor drums 1S, 1Y, 1M, 1C, and 1K by the laser beam emitted from the laser diode based on the image information sent from an external device such as a personal computer.

The photoconductor drum 1K is rotationally driven in the counterclockwise direction in FIG. 4 by a motor (not shown). The charging device 21K applies a charging bias to the charging wire to generate a discharge between the charging wire and the outer peripheral surface of the photoconductor drum 1K, whereby the surface of the photoconductor drum 1K is uniformly charged (). Charging process).
An electrostatic latent image for black is formed on the surface of the photoconductor drum 1K after charging by optical scanning of the laser beam emitted from the exposure apparatus 25 (exposure step). This electrostatic latent image for black becomes a black toner image by being developed by a developing device 22K using black toner (development step). The formed black toner image is conveyed and primaryly transferred onto the intermediate transfer belt 3 (primary transfer step).

The static elimination device 23K eliminates static electricity on the surface of the photoconductor drum 1K after the black toner image is primarily transferred onto the intermediate transfer belt 3 (static elimination step). The photoconductor cleaning device 24K includes a cleaning blade and a cleaning brush, and removes and recovers the transfer residual toner remaining on the surface of the photoconductor drum 1K that has been statically eliminated by the static elimination device 23K (cleaning step).
In FIG. 4, a series of image forming processes similar to those of the image forming unit 15K are performed in the other image forming units 15S, 15Y, 15M, and 15C, and specials are performed on the photoconductor drums 1S, 1Y, 1M, and 1C, respectively. A toner image, a yellow toner image, a magenta toner image, and a cyan toner image are formed.

The paper feed unit 18 supplies a sheet S such as transfer paper to the transfer device 4 via the paper feed path 26, and is a sheet storage unit such as a paper feed tray 27, a paper feed roller 28, and a separation roller pair 29. have.
The paper feed roller 28 feeds the sheet S located at the highest position among the sheets S loaded on the paper feed tray 27 to the separation roller pair 29 by its rotation.
The separation roller pair 29 separates the sheets S fed by the paper feed roller 28 one by one and feeds them toward the paper feed path 26. The paper feed unit 18 employs a central reference paper feeding unit that feeds sheets with reference to the center of the sheet width direction Y orthogonal to the sheet transport direction X.

The resist roller pair 30 feeds the sheet S toward the secondary transfer nip portion at the timing when the toner image forming portion on the intermediate transfer belt 3 reaches the secondary transfer nip portion of the secondary transfer portion 31. The resist roller pair 30 is divided into a plurality of pieces in the sheet width direction Y. Each paper feed path including the paper feed path 26, which is a sheet transport path, appropriately has a sheet guide member made of a thin plate member for guiding the sheet on the downstream side in the sheet transport direction X.

The transfer device 4 is arranged below each image forming unit 15, and includes a drive roller 5, a driven roller 32, an intermediate transfer belt 3, a primary transfer roller 2S, 2Y, 2M, 2C, 2K, and a secondary transfer roller 33. It has a secondary transfer facing roller 34 and a belt cleaning device 35.
The intermediate transfer belt 3 is stretched by a drive roller 5, a driven roller 32, a secondary transfer opposed roller 34, each primary transfer roller 2, etc., which are a plurality of rollers arranged inside the loop. The intermediate transfer belt 3 is driven by a drive roller 5 which is rotationally driven in the clockwise direction in FIG. 4 by a drive means (not shown), and travels while contacting each photoconductor drum 1.

Each primary transfer roller 2 is arranged so as to face each corresponding photoconductor drum 1 via the intermediate transfer belt 3, and rotates in accordance with the traveling drive of the intermediate transfer belt 3, respectively. As a result, a primary transfer nip portion is formed in which the surface of the intermediate transfer belt 3 and the surface of each photoconductor drum 1 come into contact with each other. A primary transfer bias is applied to each primary transfer roller 2 from the primary transfer bias power supply, whereby a primary transfer electric field is formed between each color toner image on each photoconductor drum 1 and each primary transfer roller 2. Then, the toner images of each color are sequentially superimposed and transferred onto the intermediate transfer belt 3 and conveyed.

The toner image formed on the surface of the photoconductor drum 1S for the special image enters the primary transfer nip portion for the special image as the photoconductor drum 1S rotates. Then, the special toner image is primaryly transferred from the photoconductor drum 1S onto the intermediate transfer belt 3 by the action of the transfer electric field and the nip pressure. In this way, the intermediate transfer belt 3 to which the special toner image is primarily transferred then sequentially passes through the primary transfer nip portions for each color image of yellow, magenta, cyan, and black, and the photoconductor drums 1Y, 1M, and 1C are sequentially transferred. , Each color toner image of yellow, magenta, cyan, and black on 1K is sequentially superimposed and transferred on the special toner image. By this primary transfer, a superposed toner image having both a full-color toner image and a special color toner image such as colorless and transparent is formed on the intermediate transfer belt 3.

The secondary transfer roller 33 rotates by sandwiching the intermediate transfer belt 3 and the sheet S between the secondary transfer opposed roller 34 and the secondary transfer roller 34. As a result, a secondary transfer nip portion is formed in which the surface of the intermediate transfer belt 3 and the secondary transfer roller 33 come into contact with each other, and the toner image on the intermediate transfer belt 3 is transferred to the sheet S and conveyed. While the secondary transfer roller 33 is grounded, the secondary transfer bias is applied to the secondary transfer facing roller 34 by the secondary transfer bias power supply.
The transfer residual toner that has not been transferred to the sheet S remains on the intermediate transfer belt 3 after the secondary transfer that has passed through the secondary transfer nip portion. The transfer residual toner is removed from the surface of the intermediate transfer belt 3 by a belt cleaning device 35 provided with a cleaning blade that is in contact with the surface of the intermediate transfer belt 3, whereby the intermediate transfer belt 3 is cleaned.

The fixing portion 19 has a heating roller 36 and a pressure roller 37 that is pressed against the heating roller 36 to form a fixing nip portion. The sheet S sent to the fixing portion 19 is sandwiched between the fixing nip portions while the unfixed toner image supporting surface is in close contact with the heating roller 36, and the toner in the toner image is melted and softened by heating and pressurizing. , The unfixed toner image is fixed on the sheet S. The sheet S on which the toner image is fixed is conveyed by a transport roller pair arranged in the paper ejection path 38, and is conveyed from the apparatus main body 16 to the outside of the machine by the paper ejection roller pair 39 arranged in the paper ejection portion 20. It is ejected and is ejected and loaded on the output tray 40.

In the above embodiment and each modification, an example in which a color printer using an intermediate transfer belt is used as an image forming apparatus is shown, but the image forming apparatus is not limited to this, and other types of direct transfer belts and photoconductors are shown. The present invention can also be applied to printers, facsimiles, copying machines, multifunction devices, and the like of transport belts using belts and secondary transfer belts. Further, in the present embodiment and the modified example, the configuration in which the sheet S is used as the recording medium on which the image is formed is shown, but the sheet S is not limited to the recording paper, and the transparency, the postcard, the envelope, the plain paper, and the like. It also includes thin paper, coated paper (coated paper, art paper, etc.), tracing paper, transparencies, transparencies, resin films, etc., and any material that can form a sheet and form an image can be used. May be good.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to such a specific embodiment, and unless otherwise specified in the above description, the present invention described in the claims. Various modifications and changes are possible within the scope of the purpose. The effects described in the embodiments of the present invention merely exemplify the most preferable effects resulting from the present invention, and the effects according to the present invention are limited to those described in the embodiments of the present invention. is not.

1 Image carrier (photoreceptor drum)
2 Multiple rollers (primary transfer roller)
3 belt (intermediate transfer belt)
4 Transfer device (transfer device)
5 Multiple rollers (drive rollers)
6 Detection means (optical sensor)
14 Image forming device (color printer)
32 Multiple rollers (driven rollers)
34 Multiple rollers (secondary transfer facing rollers)

Japanese Patent Application Laid-Open No. 2003-76111

Claims (3)

A runnable endless belt with an index on the inner peripheral surface,
With a plurality of rollers supporting the belt,
It has a detection means for detecting the index.
A transport device that controls the traveling speed of the belt based on the detection of the index by the detection means.
The endless belt is an intermediate transfer belt.
Of the plurality of rollers that support the intermediate transfer belt, one is a drive roller.
A space portion and an outer ring portion are provided in all of the plurality of rollers.
All of the plurality of rollers are divided into a plurality of rollers in the direction of the center axis of rotation.
When viewed in the direction of the rotation center axis of the roller, the detection means is arranged in a space portion of a portion divided into a plurality of parts in the rotation center axis direction of the drive roller, and the detection means arranged in the space portion is a plurality. Optical sensor,
The index and the optical sensor are transfer devices that are relatively positioned with respect to the rotation center axis. In the transport device according to claim 1 ,
The belt is movable in a direction different from the traveling direction, and the relative distance between the roller provided with the detecting means inside and the belt is unchanged before and after the movement of the belt. Device. It is equipped with an image carrier on which an electrostatic latent image is formed on the outer peripheral surface.
Claim 1 as a transfer device for transferring an electrostatic latent image formed on the image carrier to a recording medium.
An image forming apparatus according to any one of 2 to 2 , wherein the transporting apparatus is used.

Images